Internal Walls

Lightweight partitions formed from metal or timber studs are the most common method used to build the internal walls that form rooms in a home.

Advantages

Plasterboard partitions can achieve high levels of sound insulation when the correct balance of plasterboard, frame and glasswool insulation are selected. They allow for fast subdivision of a basic building envelope to form the rooms of a house or apartment.

Using glasswool insulation between the plasterboard sheets of a partition wall improves the acoustic resistance substantially because it absorbs the reverberated sound within the void inside the partition. This allows lighter and thinner plasterboards to be used which reduce the load on the structure and eases both site handling and the installation.

The reduction of reverberation within the voids when a glasswool absorbent infill layer is used also helps to cut down on the hollow sound which is characteristic of partitions where plasterboard alone is used to achieve the sound insulation required.

Knauf Insulation Products

• TP 116 is semi rigid, unfaced batt of glasswool specifically designed for friction fitting.
• Classic 040 is a roll of unfaced glasswool, available in a range thicknesses which can be used in partition walls.
• NOBASIL MPE, MPS, ADN, ADE

Detailed Design Considerations

Building Regulations

The recommended sound insulation level of internal walls within houses, flats and rooms for residential purposes is usually 40 dB Rw.

Sound Insulation

Sound insulation, otherwise known as sound reduction, is the prevention of noise being transmitted from one part of a building to another, for example by erecting a partition or wall.

When considering sound insulation between rooms in the same dwelling airborne sound is the main concern for designers.

Airborne Sound

Airborne sound sources produce noise by vibrating the air immediately around them. Typical sources include the human voice, televisions, musical instruments, sound systems and noisy dogs. 

The ability of an element of construction to resist the passage of airborne sound energy through it is largely determined by four factors:

1) The sound absorbency of any cavities in the construction.

2) The degree of structural isolation between the two outer surfaces.

3) The mass of the construction.

4) The air tightness of the construction.

Increasing the mass of a wall will improve its sound insulation, but the amount of extra weight that can be safely supported by a construction is often limited so other design approaches are usually employed i.e. absorbent materials and improved isolation.

Quality of Detailing

A wall can only achieve its expected sound performance if it and the surrounding walls and floors have no inherent faults in their detailing or workmanship. Performance will be impaired if:

• There are gaps or holes in the construction - hairline cracks or gaps can seriously impair sound insulation. Seal all potential gaps with a flexible sealant.
• There is bridging between elements that are designed to be separate. For example, a resilient bar being accidentally fixed back to a stud by the screw that secures the plasterboard to the resilient bar.
• There are gaps in the resilient layer within the cavity.

Glasswool and Acoustics

The sound absorption characteristics of glasswool make it ideal for use in partitions to assist in absorbing sound within a cavity. In addition, the thermal properties of glasswool provide a secondary benefit of minimising the heat loss between rooms within a dwelling.